1. Field of the Invention
The present invention relates to a support system of a power train of a vehicle such as automobile particularly capable of preventing a power train from being significantly moved rearward of a vehicle (i.e., vehicle body) body by an external force applied to a front portion of the vehicle without adding new components or increasing strength of a bracket or a bolt. It is to be noted that the term “vehicle” is used herein as being substantially identical to “vehicle body”.
2. Description of the Related Art
FIG. 6 shows an example of a support system of a vehicle power train that elastically supports a power train including an engine and a transmission arranged in an engine room of a vehicle such as automobile to thereby prevent vibration transmitted to a vehicle body.
In FIG. 6, reference numeral 101 denotes a left side member, reference numeral 102 denotes a left side panel, and reference numeral 103 denotes a support system. The support system 103 supports the power train disposed between a pair of left and right side members 101 (right side member is not shown) extending in a fore/aft direction (longitudinal direction or running direction) of the vehicle in an engine room. An outer cylinder 104 and a central shaft 105 both have a common axis C extending in a vertical direction of the vehicle body in a usual drivable state. A mount device 107, to which the central shaft 105 is connected to an inner periphery of the outer cylinder 104 via an isolator 106 made of rubber (rubber isolator 106), is placed on the side member 101.
In the support system 103, mount brackets 108 and 109 are secured to front and rear portions of the outer cylinder 104 of the mount device 107. The mount brackets 108 and 109 are fastened by means of bolts 112 and 113 to extension brackets 110 and 111 disposed on an upper portion of the left side member 101 with a predetermined gap therebetween in the longitudinal direction of the vehicle. The extension brackets 110 and 111 are secured to the side member 101 and the side panel 102.
In the support system 103, the central shaft 105 of the mount device 107 protrudes downward from a bottom portion of the outer cylinder 104, and a mount bracket 114 secured to the power train is connected to a lower end of the central shaft 105. In the mount device 107, a U-shaped stopper bracket 115 surrounding front, lower and rear portions of the mount bracket 114 is mounted to a lower portion of the outer cylinder 104. In the mount device 107, the mount brackets 108 and 109 are mounted to front and rear portions of the stopper bracket 115, and thus, the mount brackets 108 and 109 are mounted to the front and rear portions of the outer cylinder 104 via the stopper bracket 115.
Japanese Patent Application Laid-open Publication HEI 4-334625 (Patent Document 1) discloses one example of such a support system of a vehicle power train, which includes a structure such that, in a mount device in which a central shaft having an axis extending in a vertical direction of a vehicle is connected via a rubber isolator to an inner periphery of an outer cylinder having an axis extending in the vertical direction of the vehicle, the central shaft of the mount device protrudes downward from a bottom portion of the outer cylinder, and a mount bracket secured to a power train is connected to a lower end of the protruding central shaft.
With the structure of the vehicle in which the power train placed in the engine room in a front portion of the vehicle shown in FIG. 6 as a conventional example is supported by the support system 103, when an external force is applied to the front portion of the vehicle body, a load directed in a rear direction of the vehicle body is applied to the power train. The load is transferred to the mount device 107, the mount bracket 114, and the bolts 112 and 113 that fasten the power train and the vehicle body. When the mount device 107, the mount bracket 114, and the bolts 112 and 113 are damaged by the load, a binding force on the power train is reduced and the power train is moved toward a cabin in a rear portion of the vehicle. When the heavy power train collides with a dash panel at a predetermined speed or more, an impact force applied to an occupant is increased, thus being inconvenient and disadvantageous.
In order to reduce an amount of rearward movement of the power train of the vehicle, strength of the mount device 107, the mount bracket 114, and the bolts 112 and 113 is increased to thereby prevent them from breaking. However, when thicknesses of the mount device 107 and the mount bracket 114 are increased to ensure strength thereof, weights and cost of the mount device 107 and the mount bracket 114 are increased. Furthermore, in order to ensure strength of the bolts 112 and 113, it may be possible to increase nominal diameters or strength classifications, which however similarly increases weights and cost. Further, when strength of one component is increased, strength of the other components is relatively reduced, and accordingly, in order to increase overall strength, strength of the other components needs to be considered.
In another countermeasure, a stopper mechanism that controls a movement direction of the power train may be added to prevent the power train from being moved toward the cabin in the rear portion of the vehicle. However, it is required to newly add the stopper mechanism to reduce flexibility in layout, resulting in increasing in cost and weight.
Furthermore, in the conventional mount device 107, since a structure in which the mounting brackets 108 and 109 are directly connected to the stopper bracket 115 is adopted, when the power train significantly oscillates and the mount bracket 114 is brought into contact with the stopper bracket 115 in general use, vibration of the power train is not attenuated because of in a relatively short path but is transmitted to the extension brackets 110 and 111 on the vehicle body.